I. Field of the Invention
The present invention relates to a surface cleaning device and related method.
II. Background Information
The SCAMP.TM. underwater hull cleaning device was first introduced in 1971. In its present form, SCAMP.TM. is an underwater cleaning machine six feet in diameter and holds three large rotating brushes. Traveling across a ship's hull on three traction wheels, the SCAMP.TM. machine is either controlled by a professional diver or operated remotely to advance, stop, reverse, or hold a parallel line of motion as it makes approximately a five foot cleaning swath.
The SCAMP.TM. hull cleaning device includes a center impeller which was the subject of U.S. Pat. No. 3,906,572 issued to Winn, the contents of which are expressly incorporated herein by reference. The center impeller generates a pressure differential on the underside of the SCAMP.TM. device that allows the device to be held against the hull of a ship and that permits the three brushes to rotate at approximately 120 rpm with the sole purpose of optimizing cleaning and minimizing paint damage. Other prior art hull cleaning machines operate their brushes at relatively higher speeds in order to create a centrifugal force to clamp the machine against the ship's hull. In addition, the use of the clamping impeller as shown in the Winn patent permits a wider inventory of brush configurations than that available on machines without center impellers. Specifically, the Winn configuration permits brushes to operate employing the sides of the brush bristles. Cleaning is accomplished by a scything action rather than a harsh scrubbing with the tips of the stiff bristles as is common with other apparatus and related methods. As a result, the prior SCAMP.TM. device does not damage functioning protective coatings to the extent those coatings may be at risk with more conventional prior art devices.
Due to the saucer shape of the SCAMP.TM. housing and the action of the impeller, the device clamps to the hull surface with a net clamping force of about 570 kgf. The traction effect on the wheels is approximately 204 kgf so that the SCAMP.TM. underwater hull cleaning device can be used effectively against tidal forces of up to three knots. The SCAMP.TM. underwater hull cleaning device had been approved for use at oil tanker terminals as well as in harbors with stringent environmental controls. Its use is desirable because independent studies have shown that this operation was thought not to impact meaningfully on the quality of the waters of an estuary or harbor.
The prior art SCAMP.TM. device, however, has no provision for collecting debris or effluent which may result from the underwater hull cleaning operation. Rather, the prior art SCAMP.TM. device simply discharges a plume of water back into the sea.
In the intervening years since the introduction of SCAMP.TM., underwater hull cleaning has changed significantly. The chemical composition of underwater paint has been modified, whereby copper and cuprous oxide (in depleted paint, and also attached to marine growth) may be released by underwater cleaning. In addition, the passage of the Clean Water Act has heightened concern among various federal and state environmental agencies regarding the potential impact of hull cleaning on the ambient water.
Thus, the process of underwater hull cleaning is being subjected to extensive evaluation with respect to its potential impact on the environment. In fact, pending certain test results, underwater hull cleaning of painted surfaces is temporarily suspended in certain ports. Accordingly, one Navy laboratory has contracts in place to develop an automated hull maintenance vehicle (AHMV), seeking the design of a new machine with the ability to effectively collect debris and effluent. The assignee of the present invention is a subcontractor to two principal contractors for this effort. However, the present invention was conceived and developed without the benefit of any government funds.
Competitors to the assignee have also developed hull cleaning apparatus. For example, U.S. Pat. No. 5,174,222 discloses an apparatus for cleaning ship hulls known commercially as the SEAVAC.TM. device. As may be seen in the '222 patent, the SEAVAC device employs the same general concept of a center impeller to hold the machine against the hull of a ship during the cleaning process. However, as is true with the prior SCAMP.TM. design, the SEAVAC device has no ability to collect debris and effluent.